Neeed help urgent

Ifurniture stores having a weekend sale and is offering 20% discount on patio chairs and table the sales tax on furniture is 6.25 using function composition how can you represent the total amount a that you would need to pay for this furniture that cost x dollars

Solve for b. ab + c= d b= a + old ob=allc-ch b= (d-c/a

What are the solutions of the equation x4 – 5x2 – 14 = 0? use factoring to solve. someone !